As a conventional electrostatic coating device, there is known an electrostatic coating device in which a reserve portion for temporarily storing a conductive coating medium is disposed in a coating medium supply passage for supplying a coating medium from a coating medium supply portion to a spray gun and the coating medium supply passage is cleaned when a color of the conductive coating medium is switched (for example, see JP-A-2004-275976).
FIG. 14 is a view illustrating a known electrostatic coating device 100. Hereinafter, an operation of the electrostatic coating device 100 shown in FIG. 14 will be described.
In order to perform an electrostatic coating operation, first, switch valves 112 and 114 of a block valve mechanism 106 are opened to connect supply passages 111, 113, and 123. For example, a coating medium valve 102 of a color switch valve mechanism 105 is opened and a servo motor 134 of an intermediate reserve tank 107 is driven so that a piston 126 is moved in an A1 direction.
As a result, a conductive coating medium of a predetermined color passes the supply passages 111, 112, and 113 from a coating medium valve 102 and is then filled in a cylinder chamber 128. At this time, a second dump valve 141 and a trigger valve 142 are closed.
Next, the switch valve 114 is closed, the trigger valve 142 is opened, and the servo motor 134 is driven so as to move a piston 126 to an A2 direction. As a result, the conductive coating medium is extruded under pressure from the cylinder chamber 128 to a transmission passage 137. Subsequently, the conductive coating medium passes through the trigger valve 142 and is sprayed from a spray gun 108. At this time, a high voltage is applied to the conductive coating medium and then an electrostatic coating operation is performed on a coating object (not shown).
When the electrostatic coating operation is performed, and then the electrostatic coating operation with the coating medium of a different color is performed, the second dump valve 141 and the trigger valve 142 are opened. At this time, a cleaning operation is performed by connecting the supply passages 111, 113, and 123 and by opening a first cleaning valve 101 so as to flow a cleaning solution into the supply passages 111, 113, and 123, the intermediate reserve tank 107, the transmission passage 137, and a third ejection passage 144 and to spray the cleaning solution.
At this time, the coating medium supply passage can be cleaned partly, but it is not economical in that the unused coating medium remaining in the coating medium supply passage is wasted. Accordingly, it is desirable to further reduce an amount of the coating medium remaining in the coating medium supply passage.